Sample observation device and sample observation method

1. An observation device for observing a sample, the observation device comprising:

an illumination optical system; and

an observation optical system,

wherein:

the illumination optical system includes a light source, a condenser lens, and an aperture member,

the observation optical system includes an objective lens and an imaging lens,

the aperture member has a light-shielding part or a darkening part, and a transmission part,

the aperture member is disposed so that the light-shielding part or the darkening part includes an optical axis of the illumination optical system,

the transmission part is located outside of an outer edge of the light-shielding part or the darkening part,

an image of the transmission part of the aperture member is formed approximately at a pupil position of the objective lens,

an image of an inner edge of the transmission part is formed inside of an outer edge of a pupil of the objective lens,

an image of an outer edge of the transmission part is formed outside of the outer edge of the pupil of the objective lens,

when the sample is present, the image of the transmission part is decentered relative to the pupil of the objective lens due to refraction caused by the sample, and

the following conditional expressions are satisfied:

0.005≤Ratio≤0.9, and

1.1≤ I 0.1 /I 0

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes a length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes a length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes a radius of the pupil of the objective lens;

β denotes a value obtained by dividing a focal length of the objective lens by a focal length of the condenser lens;

I 0.1 denotes a quantity of light passing through the pupil of the objective lens when Δd=0.1×R ob ;

I 0 denotes a quantity of light passing through the pupil of the objective lens when Δd=0; and

Δd denotes an amount of displacement of the image of the transmission part of the aperture member relative to the pupil of the objective lens.

2. The sample observation device according to claim 1 , wherein the following conditional expression is satisfied:

0.015≤Ratio≤0.9

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

3. The sample observation device according to claim 2 , wherein when 1.02≤R 1 ×β/R ob <1.05, the following conditional expression is satisfied:

0.1≤Ratio≤0.9

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

4. The sample observation device according to claim 2 , wherein when 1.05≤R 1 ×β/R ob <1.15, the following conditional expression is satisfied:

0.05≤Ratio≤0.8

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

5. The sample observation device according to claim 2 , wherein when 1.15≤R 1 ×β/R ob <1.3, the following conditional expression is satisfied:

0.025≤Ratio≤0.7

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

6. The sample observation device according to claim 2 , wherein when 1.3≤R 1 ×β/R ob <1.6, the following conditional expression is satisfied:

0.015≤Ratio≤0.6

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

7. The sample observation device according to claim 2 , wherein when 1.6≤R 1 ×β/R ob <2, the following conditional expression is satisfied:

0.015≤Ratio≤0.5

where:

Ratio=(R ob −R 0 ×β)/(R 1 ×β−R ob );

R 0 denotes the length from the optical axis of the illumination optical system to the inner edge of the transmission part;

R 1 denotes the length from the optical axis of the illumination optical system to the outer edge of the transmission part;

R ob denotes the radius of the pupil of the objective lens; and

β denotes the value obtained by dividing the focal length of the objective lens by the focal length of the condenser lens.

8. A method of observing a sample comprising:

emitting, to the sample, light flux with a predetermined width intersecting an optical axis of an objective lens,

wherein:

the light flux with the predetermined width reaching a pupil position of the objective lens satisfies the following conditions (A), (B), and (C) when the sample is absent:

(A) innermost light of the light flux with the predetermined width is positioned on an inside of a pupil of the objective lens;

(B) outermost light of the light flux with the predetermined width is positioned on an outside of the pupil of the objective lens; and

(C) an image of a transmission part of an aperture member that limits the light flux is formed near the pupil of the objective lens, and a width of the light flux positioned on the inside of the pupil of the objective lens is not less than 0.005 times and not more than 0.9 times a width of the light flux positioned on the outside of the pupil of the objective lens;

when the sample is present, the image of the transmission part is decentered relative to the pupil of the objective lens due to refraction caused by the sample; and

the following conditional expression is satisfied:

1.1≤ I 0.1 /I 0

where:

I 0.1 is a quantity of light passing through the pupil of the objective lens when Δd=0.1×R ob ;

I 0 is a quantity of light passing through the pupil of the objective lens when Δd=0;

Δd is an amount of displacement of the image of the transmission part of the aperture member relative to the pupil of the objective lens; and

R ob is a radius of the pupil of the objective lens.